Organization of diencephalic projections from the spinal trigeminal nucleus oralis: An anterograde tracing study in the rat

The organization of the efferent projections from the spinal trigeminal nucleus oralis (Sp50) to the diencephalon was studied in the rat using the anterograde tracer Phaseolus vulgaris leucoagglutinin. The present study confirms the existence of trigemino-thalamic pathways originating from the Sp50 and details their distribution. The main diencephalic targets of the Sp50 are the ventral posteromedial thalamic nucleus (VPM), the posterior thalamic nuclei (Po) and the ventral part of the zona incerta (Zlv), contralaterally, and the parvicellular part of the ventral posterior thalamic nucleus (VPpc), bilaterally. The distribution of these projections varies according to the dorso-ventral location of the injection sites: the dorsal part of the Sp50 projects to the medial part of the VPM and the Po, and to the caudal part of the Zlv, as well as to the VPpc. The ventral part of the Sp50 projects to the lateral part of the VPM and the Po and to the rostral part of the Zlv. These results suggest that the trigemino-diencephalic pathways originating from the Sp50 are involved in the processing of gustatory and somatosensory information. (C) 2004 IBRO. Published by Elsevier Ltd. All rights reserved.